Welcome to the forum!
Glad you are here!
It would help to have an idea about how old they are. If they are laying, it doesn't matter but if they are not laying, it would help. There are still lots of things you can do, even if yu don't know how old they are.
Food comes in three textures, mash, crumbles and pellets. Just because it is one or the other doesn't really tell you a lot. They make it in pellet form, then crush it to get it down to crumbles, or may grind the pellets to get a finer texture for mash. What is important is that they have different requirements based on age. Texture really does not matter. From hatch until 6 weeks old, they need Starter. That is around 18% to 20% protein, can't remember exactly. From 6 weeks old until 20 weeks old or they start to lay, they need Grower, which is about 16% protein. Then, from 20 weeks or when they start laying, they need Layer. It is also 16% protein but it has just over 4% calcium which they need for the egg shells. Too much calcium can hurt young growing chickens. Grower typically has a little over 1% calcium, which is plenty for bone development but not enough to hurt a growing chick.
If you really don't know their age and they are not laying, I'd suggest feeding them 16% Grower, but also offer them oyster shell on the side. Oyster shell is really high in calcium. If they need calcium, they'll eat it. Some people will make it more complicated, but this is the simplest way I know of to give them what they need and not give them anything that will hurt them. Most Grower comes in crumbles form around here.
There is a lot of discussion on heat in the coop on this forum. I'm in the group that believes you do not normally need to provide heat unless you are really in extreme circumstances. Freezing weather is not extreme. Remember that chickens are wearing down coats. They really can handle pretty cold temperatures as long as they have good ventilation and are not in a direct draft. My chickens will go outside and play in single digit temperatures as long as they are not in a wind. To me, the risks in winter is when a breeze is hitting them when they are sleeping or the moisture or ammonia builds up in the coop due to poor ventilation. I don't know what the coop they are in looks like so I can't definitely say you won't have any problems, but I suggest you talk to the owners about what they do. You may find out that the chickens do OK with minimal help.
Hope this helps some and again
